The mammalian brain is an immensely complex organ in terms of diversity of resident cell types, anatomical organization, neuronal circuitry, modes of intercellular communication, and the regulation of protein expression. Further the effect aging and Alzheimer's disease (AD) has on the brain represents a colossal challenge for researchers. Previous mass spectrometry based proteomic technologies have been most adept at identifying protein-protein interactions or post-translational modifications of enriched proteins from a single cell type. The recent development of in vivo isotopic labeling of mammals and high resolution mass spectrometers has afforded the opportunity to determine the relative protein expression level of thousands of proteins from tissue. We aim to calculate changes in protein expression during Alzheimer's disease progression and regular aging in the mammalian brain by quantitative mass spectrometry. This project will yield a large-scale anatomic inventory of protein expression on an unprecedented level which can be mined for years to come. These quantitative proteomic studies will serve as a hypothesis-generating machine that will likely uncover new and unexpected data on the effect aging and AD have on the brain. Those in the advanced stages of AD become bed-bound and reliant on care 24/7 which in total results in 148 billion dollars in annual costs in the US alone. The effect of aging and AD on brain physiology has been historically investigated in candidate-based approaches. While these candidate approaches have significantly contributed to our understanding of aging and AD, they have been limited by their restricted scope. To broaden our knowledge base of these processes and eventually develop effective therapeutics for the treatment of AD we will calculate the expression level for thousands of proteins. Proteins with perturbed expression will serve as beacons for the identification of pathways relevant to AD pathology and aging. Determination of perturbed pathway(s) will in turn serve as fertile ground for in-depth analysis aimed at deciphering the molecular basis of AD and aging. More generally, this project will deliver a brain atlas of protein expression that occurs during aging and AD. AD represents a significant threat to the aging world population: AD is considered the world's most common neurodegenerative disease, affecting over 5 million aging Americans, and is a rising threat to public health. AD debilitates individuals by stripping them of the ability to reason, use language, and recall memories, resulting in a tremendous caretaking burden. Currently there is no cure or definitive treatment for AD and it remains the leading cause of dementia. AD is stratified by the age at which pathological onset occurs. The two forms of AD, early-onset and late-onset, both have genetic links. Identification of new genes and/or proteins that contribute to AD pathology could provide a critical first step for the development of effective AD treatments.